#include <bits/stdc++.h>
using namespace std;
int n, m;
const int maxn = 2504;
int chainw[maxn][maxn];
int chainh[maxn][maxn];
int getParentW(int i, int j) {
if (chainw[i][j+1] != 0) return getParentW(i, j+1);
return j;
}
int getParentH(int i, int j) {
if (chainh[i+1][j] != 0) return getParentH(i+1, j);
return i;
}
int main() {
cin >> n >> m;
int all0 = true;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
char x;
cin >> x;
if (x == '1') {
all0 = false;
chainw[i][j] = chainw[i][j-1]+1;
chainh[i][j] = chainh[i-1][j]+1;
}
}
}
if (all0) {
cout << 0 << endl;
return 0;
}
int maxpossiblew = maxn;
int maxpossibleh = maxn;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
j = getParentW(i, j);
if (chainw[i][j] == 0) continue;
maxpossiblew = min(maxpossiblew, chainw[i][j]);
}
// if (maxw[i] == 0) continue;
// maxpossiblew = min(maxpossiblew, chainw[i][maxw[i]]);
}
for (int j = 1; j <= m; j++) {
for (int i = 1; i <= n; i++) {
i = getParentH(i, j);
if (chainh[i][j] == 0) continue;
maxpossibleh = min(maxpossibleh, chainh[i][j]);
}
// if (maxw[i] == 0) continue;
// maxpossiblew = min(maxpossiblew, chainw[i][maxw[i]]);
}
cout << maxpossibleh * maxpossiblew << endl;
return 0;
}
